In the past, see for example German patent document DE 22 35 537, the fiber raw material was comminuted in a dry state to produce the fibers which were then mixed with the binder and water. The binder used is generally a finely divided hydratable binder, i.e. a binder which reacts in the presence of water of hydration to form a hydrated form which solidifies.
Such mixtures are shaped by pressure to form the shaped article which can be of sheet, slab, brick, block or structural shape, such as that of a girder, or some other shape, like that of a pipe, used in building construction or the like. In some cases, apart from pressure, it is also possible to use heat in shaping and setting the finished article.
In the prior technique described, the fiber raw material and the hydratable binder may be milled together and thereby also mixed, the milling serving to break up the fiber raw material to produce the fibers. The fiber raw material can be subjected to comminution independently of its mixing with the hydratable binder and then mixed with the latter. In both cases, the water of hydration is added after the mixing of the dry ingredients.
The problem with such systems, in which the water of hydration is added after a mixture of the dry ingredients, is that agglomerates easily are produced and these may detrimentally influence the parameters of the product, the homogeneity of the shaped article, strength and the like.